Inertia, to most people, means lack of motion. Physicists add another definition: the property of a moving object to continue in the same direction unless acted upon by an outside force.
Both kinds of inertia, unfortunately, characterize the nation's response to the threat of nuclear war. On the one hand, we continue to expand our arsenals; on the other, we think only sluggishly about changing course.
Which is why a book like Harold Willens's ''The Trimtab Factor'' is useful. Thin, high-pitched, frequently alogical, it is also provocative. Its goal: to activate the business community on nuclear issues.
Mr. Willens's title comes from Buckminster Fuller's description of the small rudder attached to the main rudder on a large ship. Turning the large rudder - fighting the inertia of a moving vessel - requires major effort.But turning the trimtab is easy. It then turns the main rudder, which turns the ship - an example, says Mr. Willens, of how ''the precise application of a small amount of leverage can produce a powerful effect.''
His point: The business community must apply that kind of leverage to politicians on nuclear arms.
Mr. Willens has the credentials to address this constituency. A former United States Marine officer, the Ukrainian-born millionaire spearheaded the nuclear freeze initiative in California's 1982 election. To be sure, his book has its flaws. Lunging at the problem with zealous oversimplification, he stumbles into self-contradictions - as when, after lambasting the concept of deterrence, he argues that the Soviets will not expand into Europe because of ''the probability of a recourse to nuclear weapons by the Western powers.''
The book's real value, instead, comes in its articulation of the economic arguments against nuclear weaponry. Attacking the idea that an arms race is good for business, Mr. Willens notes that:
* The nation's economic decline results from military spending that, for three decades, has consumed nearly 50 percent of the federal discretionary budget.
* Defense spending produces ''dead-end dollars'': Putting money into pockets without putting consumer goods on the shelves, it simply fuels inflation.
* Research studies show that ''a billion dollars spent for military purposes generates far fewer jobs (eighteen thousand) than the same billion dollars spent in the civilian industrial sector (twenty-seven thousand).''
Through these sorts of bottom-line arguments, the book, like a trimtab, helps steer the antinuclear argument out of left-wing waters (where it has drifted for years) and into sea lanes more acceptable to the right. Yet against Mr. Willens's faith in the businessman's solution must come a caution: Any genuine sea change in the nuclear arms race requires a far deeper shift than his book proposes. ''The unleashed power of the atom,'' Mr. Willens quotes Albert Einstein as saying, ''has changed everything except our way of thinking.''
And that, sadly, is the change most nuclear-freeze advocates (Mr. Willens among them) have yet to articulate. For the nuclear threat is only a symptom of humanity's plight. The underlying cause? The dimly seen but widely held belief that peoples and nations are most effectively ruled by fear. It's a deadly misconception. It's a notion that says that mankind can best be motivated (politically, theologically, educationally, and morally) by the dread of punishment - and by the deterrence (nuclear or otherwise) that arises from that dread.
That's an old dragon; it will die hard. Until it does, we'll continue imagining that the more we scare our enemy, the safer we will be. Sometimes the enemy will be a Kremlin leader. More often it will be an urban criminal, or a truculent salesgirl, or an obstreperous child. We deal with each in the same way, hoping to inspire the dread that deters. Small wonder we're so scared.
Could it be that the real trimtab factor is the recognition that peace arises not from withholding something dreaded but from sharing something desired? Interestingly enough, that sense of sharing - providing a good or service to fill a need - underpins the best elements of the commercial world. So Mr. Willens's choice of constituency may be right: The business community, used to sharing the good rather than threatening the bad, may be just the force needed to turn the ship around.